Si-Based Nanofiber Anodes for Li-Ion Batteries Prepared Using Particle/Polymer Electrospinning

The demand for rechargeable batteries with high energy and power densities has never been greater. The functionality of many portable electronic devices is limited by battery size and lifetime. Similarly, electric vehicle propulsion systems require significant improvements to satisfy consumer expectations for long drive distances and short recharge times. To meet the demands of energy-hungry consumers, new battery electrodes with high capacities and long cycle life at fast charging rates must be developed.^[1-2] These requirements have motivated research efforts to develop next-generation Li-ion battery materials, such as nano-structured silicon anodes. There is also a need for new electrode architectures to replace conventional slurry cast materials. One approach for an electrode design is the use electrospun electrodes containing engineered void spaces to enhance Li⁺ transport rates for high areal capacities at fast charge/discharge rates.

Silicon has received considerable attention as an active material for Li-ion battery anodes due to its high theoretical capacity (3,579 mAh/g vs. 372 mAh/g for graphite). However, silicon based anodes typically suffer from rapid capacity fade due to particle cracking and electronic isolation caused by large volumetric changes between the lithiated and delithiated states. While particle fracture can be eliminated by using nanosized Si, electronic isolation remains problematic. Another significant obstacle for commercialization of Si in Li-ion batteries is the irreversible consumption of Li during formation of the solid-electrolyte interphase (SEI) layer.

The present work is the latest installment by Pintauro and co-workers on the use of particle/polymer electrospun nanofiber mats for fuel cell and Li-ion battery electrodes.^[1-5] Such electrodes are a viable and attractive alternative to electrospun mats prepared by carbonizing polymer fiber precursors at high temperature. In particle/polymer electrospinning, there is no fiber pyrolysis; the electrospinning and post-processing are performed at room temperature which simplifies the process and preserves the beneficial characteristics of the polymer binder. Furthermore, the structure of the fibers can be easily altered for improved battery performance (e.g., by using core-shell or hollow-bore fibers or fibers with a high internal porosity). Due to these characteristics, high gravimetric, areal, and volumetric storage capacities can be achieved through the use of thick, densely packed particle/polymer nanofiber mats.

In this presentation, recent results will be presented on the fabrication and use of electrospun particle/polymer nanofiber anodes containing Si nanoparticles, carbon powder, and poly(acrylic acid) binder (Si/C/PAA). Charge/discharge properties of the nanofiber electrodes will be presented, and electrode capacities for different fiber mat thicknesses and mat porosities will be discussed. Notably Si/C/PAA nanofiber anodes have been prepared with high gravimetric, areal, and volumetric capacities of 1,100 mAh/g, 3.1 mAh/cm², and 560 mAh/cm³, respectively, which were stable for 50 cycles at 0.1C. These results demonstrate that proper micron-scale design of electrodes can enhance Li-ion battery performance.

References

1. E. C. Self, R. Wycisk and P. N. Pintauro, Journal of Power Sources, 282, 187 (2015).

2. E. C. Self, E. C. McRen, and P. N. Pintauro, ChemSusChem, 9, 208 (2016).

3. W. Zhang and P. N. Pintauro, ChemSusChem, 4, 1753 (2011).

4. M. Brodt, R. Wycisk and P. N. Pintauro, Journal of The Electrochemical Society, 160, F744 (2013).

5. M. Brodt, T. Han, N. Dale, E. Niangar, R. Wycisk and P. Pintauro, Journal of The Electrochemical Society, 162, F84 (2015).